Process for conferring antistatic properties to synthetic textile fibers



United States Patent 6 PROCESS FOR CONFERRING ANTISTATIC PROP- ERTIES TO SYNTHETIC TEXTILE FIBERS No Drawing. Application June 1, 1955 Serial No. 512,566

Claims priority, application Netherlands July 1, 1954 Claims. (Cl. 117-76) This invention relates to a process for rendering antistatic products not conducting electricity, i.e., having dielectric properties.

One of the principal objects of the present invention is to provide a new and improved method for treating non-electrically-conductive products, whether in the form of threads, fibers, foils, yarns, knitted and woven textile articles, etc., in such manner as to render them substantially completely antistatic.

A further object of the invention is to provide a method for treating such products for the purpose indicated in order to confer upon them antistatic properties that will persist despite subsequent treating operations to which the products may be subjected, such as washing, dyeing, etc.

The manner in which these and other objects and features of the invention are attained will appear more fully from the following description thereof, in which referonce is made to typical and preferred procedures in order to indicate more fully the nature of the invention, but without intending to limit the invention thereby.

Products not conducting electricity have the property that they become electrostatically charged during further processing and during use. These electrostatic charges, which may occur by rubbing the products against each other or by rubbing the products with other bodies, give rise to various disadvantages which may show themselves in different ways dependent upon the nature of the treatment or the use.

The electrostatically charged products may e.g. repel each other but they may also attract and hold dirt, dust, etc.

As examples of products not conducting electricity and which may be treated according to the process of the invention may be mentioned threads, fibers, cables, yarns knitted and woven textile articles, as Well as bristles, films, foils and products obtained by injection molding or by any other manner from synthetic hydrophobic polymers, such as polyamides, polyesters and polyacrylonitrile derivatives. Furthermore, dielectric products manufactured from glass and porcelain may also be mentioned.

When an artificial thread or the like made from synthetic, hydrophobic polymers such as mentioned above is guided over guide means, such as guiding eyelets, guiding bars, thread brakes, etc. the friction that is unavoidably encountered creates charges upon the filaments and threads so that they repel each other thus giving rise to processing difficulties and sometimes even failures.

Staple fibers which must be spun to yarns can only with difficulty be carded due to the occurrence of electrostatic charges.

Even in ordinary use, hose or garments made from said threads or fibers attract dust and are very persistent in retaining said dust. Frequently runners and rugs retain dust and dirt so strongly that they cannot be cleaned by brushing, beating or vacuum cleaning.

To prevent the occurrence of static charges it has already been proposed to treat synthetic, hydrophobic threads, etc. with various preparations. However, since said preparations are more or less readily washed away the products treated therewith quite rapidly lose their antistatic property on dyeing or washing; and fu1thermore even without washing the antistatic effect diminishes substantially after a relatively short time.

According to the present invention it has been found possible to apply to non-electrically-conductive products a stable antistatic surface layer.

The process according to the present invention is characterized in that the products are treated with an aqueous solution of a polymeric, polyanion-active substance which loses its solubility in water by heating above C., after which the thus pre-treated products are dried and subsequently heated above 100 C., whereupon the products are then treated with an aqueous solution of a cation-active soap, and finally are dried.

It is preferred to use polymeric, polyanion-active substances having carboxylic acid radicals, and polyacrylic acid has proved to be very suitable.

However, the treating agents employed in the process according to the present invention generally exhibit strongly adhesive properties, so that by contact with one another or by contact with other bodies during the drying and the heating operation the products treated therewith have a tendency to adhere to each other. In cases where the objects or elements are treated individually, such as is possible in the case of monofils, films and articles, and in some cases with textile material, this is not inconvenient. In other cases, especially in cases where filaments or threads must remain loose from each other, i.e., more or less readily displaceable with respect to each other, this adhesion causes difiiculties and so according to a further feature of the invention an anion-active soap which is soluble in water and lowers the surface tension is added. Said anion-active soap acts as an anti-adhesive agent and it has been found that such a soap in the proportion of about 1/ 10 of the concentration of the polyanion-active substance is sufficient to prevent the undesired adhesion.

It has been found that the sodium salt of oleylmethyltauride is especially suitable as the anti-adhesive agent.

The heating that follows the treatment with. the polyanion-active substance is preferably done at temperatures between and C.

Based on the disclosure herein, it becomes a relatively simple matter for one skilled in the art to determine which polyam'on-active substances are suitable for use in the process according to the present invention. This can be directly determined by heating a small amount of the dry polyanion-active substance above 100 C. to determine whether said substance is thereafter soluble or insoluble in water. Polyanion-active substances which after heating above 100 C. remain soluble in water are not suitable. Those substances which after heating above 100 C. be come insoluble may be used.

As indicated above, polyanion-active substances having carboxylic radicals may be used. However, metal salts thereof such as the sodium salts are not suitable since even after heating the latter at a temperature of 120-1S0 C. they still remain soluble in water.

While the ammonium salts of the polya'nion-active, polymeric acids are generally suitable, nevertheless the corresponding polycarboxylic acids are preferred.

Although polyacrylic acid has been found to be very useful for use in connection with the present invention, this is not the case with polymethacrylic acid and also not with the sulphonic acids of polystyrene. The latter products do not lose their solubility in water on heating above 100 C., and are therefore not suitable.

The optimum concentration for the first treating bath may be readily determined experimentally since it has been found preferable to keep the amount of substance applied between certain limits. These Concentration lim us are dependent upon the kind of polyanion-active substance employed and the shape of the product: to be treated. On treating threads or fibers with a solution of polyaerylic acid, a concentration of 1% by weight is generally sufiicient.

The first treating bath may be sprayed in warm condi' tion on the product or it may be applied to the product by means of rollers. If feasible, it is generally preferred to use the immersion process.

The temperature of the first bath is preferably kept between 70 and 90 C. The duration of the treatme'ntris not critical since it is only necessary to have a good impregnation which generally takes place in a few seconds or even in a shorter time.

The products treated with the first treating bath mayif desired and dependent upon the shape thereof-be centrifuged, pressed-out or be subjected to vacuum for removing excess treating liquid, or the excess may be removed by any other convenient means as may be desired.

The products treated in this manner are then dried at relatively low temperatures and then baked at a temperature above 100 C. It is of course obvious that the baking temperature must be below the melting point of the product to be treated.

The duration of the heating not only depends upon the specific treating substances but also upon the baking temperature and the mass of the product undergoing treatment. The heating is continued until the necessary insolubility of the surface layer is obtained. It is of no use to continue the heating further. The necessary treating duration may be readily determined experimentally. Care must be taken that no discoloration of theproducts takes place in instances Where this might detract from the value of the final product. if discoloration of the final product is to be avoided care must be taken that the substances used in the treatment do not give discoloration on heating.

After the heating or baking there are still anion-active groups present and with regard thereto, according to a further feature'of the invention, a further treatment is effected with an aqueous solution'of a cation-active soap after the baking.

It has been found that amongst others, quaternary compounds, such as alkyltrimethylarnmonium compounds and alkylpyridinium compounds, are suitable as the cation-active soaps. Also quaternary compounds of sulphur, phosphorus, arsenic, antimony, and also, under special conditions, quaternary compounds of oxygen may be-used;

It has been discovered that the quaternary ammonium compound stearyltrimethylammoniumchloride is especially suitable.

The quaternary alkylammonium compounds have the advantage over the corresponding quaternary alkylpyridinium compounds that the former do not give a discoloration or yellowing of the products.

The treatment with the second bath is done in the same manner as the treatment with the first bath. Preferably, the treatment is done at low temperatures but if if necessary the treatment may be done, for example, at' 50 C. in order to prevent clouding of the cationa'ctive" soap solution.

Since the pretreated and baked product has an acid reaction itis preferred to bring the treating bath to the correct pH so as to obtain a final product that reacts neutral.

It was found that the reaction of the cation-active soap with the anion-active groups on the baked produc proceeds very rapidly. r

In many cases it is preferred to remove the residual cation-active substance which has not reacted with the anion-active groups. It was found that this may be done satisfactorily by rinsing immediately after the treatment with the cation-active soap. Especially with textile materials a rinsing after the treatment is very desirable.

The drying after the treatment is done in a normal manner.

The different treatment substances show with relation to the final effect always certain differences and especially with regard to the stability of the antistatic layer. Thus, the various cation-active soaps give with one and the same polymeric, polyanion-active primary treatment substance different results.

When using polyacrylic acid as the polymeric, polyauionactive substance an aftertreatrnent with lauryltriethylammoniumchloride gives a surface layer which is stable against hot water but which may be washed away with hot, dilute'acid or alkaline soap solutions.

Under the same circumstances stearylamine-acetate, i.e., the acetic acid salt of stearylamine, gives a surface layer which has relatively good stability against hot later and dilute acids, although not against alkaline soap solutions.

Under the same conditions, however, stearyltrimethylammoniumchloride gives a surface layer which has good resistance against hot water, dilute acids and alkaline soap solutions.

By resistance against dilute acids is meant that the formed surface layer resists a prolonged treatment with a 0.4% solution of formic acid or sulfuric acid such as is sometimes used in dyeing operations.

By resistance against soap solutions is means that the formed surface layer resists a prolonged and/or repeated washing with a solution containing 0.2% soap and 0.2% sodium carbonate.

It was found that the strength of the products, includ ing fibers and threads, is not markedly diminishedby treatment according to the present invention. 7

Dyed as well as undyed products may be satisfactorily treated according to the process of the present invention. A great advantage is that the treated undyed products may be dyed later on without losing their antistatic properties.

it should be noted that on applying the process accord ing to the present invention to fibers and threads made from glass, the advantage is also obtained that the antistatic layer may be dyed. It is also possible'to add a dye or pigment to the first bath and to obtain directly in this manner a colored antistatic layer. 7

Weblike, permeable textile products such as warps of threads in which the threads are, spaced some distance and parallel to each other, webs of fabrics and paper'- like, non-permeable elongated products, such as films and foils, made from the basic materials mentioned, may

be guided continuously by means of suitable rollers through the treatment baths, drying device and baking device. Before drying they may be freed from excess liquid in any convenient manner as desired.

In order to indicate still more fully the nature of the present invention, the following examples of typical procedures are set forth, it being understood that this description is presented by way of illustration only, and not as limiting the scope of the'invention.

Example I In an aqueous solution containing 1.0% by weight of polyacrylic acid and 0.1% by weight of the sodium salt of oleylmethyltauride, 10 kg. polyamide fibers (titrei 4.5 den., and staple length: 110 mm.) were immersed. The temperature of the bath was C. The bath ratio was 1:16, and the fibrous mass was treated while stirring centrifuged to a" moisture content of about 20%. Subsequently'the masswasdried for two hours in aw'ell opened Thereafter, the mass was and divided condition at 60 C. and thereafter baked for 20 minutes at 140 C.

The thus-treated fibers were further treated while stirring for 15 minutes in a second bath containing 0.5% by weight of stearyltrirnethylarnmonium chloride. The temperature of the bath was 45 C. and the bath ratio 1:16. Thereafter the fibrous mass was centrifuged, carefully rinsed, again centrifuged and finally dried at 60 C.

The fiber so obtained could be easily carded and it was possible to process said fiber in an easy manner to de sirable yarns, intermediate products and final products. The articles manufactured did not, for all practical purposes, show the disadvantage of attracting dirt and dust, or to hold dirt or dust.

The layer provided on the surface of the fiber could not be washed away by treatment with hot water, hot dilute acids and warm alkaline soap solutions. The layer applied Was also resistant against the usual treatments, such as dyeing, washing, etc.

Example II In an analogous manner to that described in Example I, an amount of kg. fibers from polyethyleneterephthalate was treated. Notwithstanding the fact that the polymer from which the fiber was manufactured had an entirely different molecular structure than that of the fiber of Example I, the treated fiber showed completely analogous effects in comparison with the product treated according to Example 1.

Example 11] A web of shirt material, manufactured from a superpolyamide obtained by polymerization of s-caprolactam (Td 50/10), having in the warp as well as in the weft 60 threads of 50 denier (10 filaments) per cm., was soaked on a triple roller device with a solution of 1.0% by weight of polyacrylic acid and 0.1% by weight of sodiurnoleylmethyltauride in water. The solution was kept at a temperature of 80-90 C. The pressing-out effect was about 40%.

After drying, the Web was heated under tension at 190 C. and for a period of 20 seconds. In this manner the baking of the applied layer and the known stabilization of the polyarnide fabric was combined in one operation. Subsequently, the fabric was impregnated in a triple roller device with an aqueous solution containing 0.5% stearyltrimethylammoniumchloride. The pressing-out effect here was about 45%.

After rinsing the fabric and finally drying on a tenter, no electrostatic charge could be observed by rubbing after conditioning. V

The fabric, the color of which had remained unchanged, retained its antistatic character even after 40 washings in a warm solution of 0.2% sodium soap and 0.2% sodium carbonate.

Although the antistatic layers obtained by the process according to the present invention show varying stabilities in some respects, it was observed that in course of time the initially-obtained antistatic action was not lost. This is contrary to the results obtained with the usual treatments for making products antistatic where the initially-obtained antistatic action diminished after some time.

While specific examples of preferred methods and products embodying the present invention have been described above, it will be apparent that many changes and modifications may be made in the methods of procedure and products without departing from the spirit of the invention. It will therefore be understood that the examples cited and the methods and products set forth above are intended to be illustrative only, and are not intended to limit the invention.

What is claimed is:

1. A process for imparting antistatic properties to high molecular weight synthetic polymeric fibers, the steps consisting essentially of treating the fibers with an aqueous solution of polyacrylic acid at a temperature less than C., thereafter drying the thus pre-treated fibers, subsequently heating them to an elevated temperature above 100 C., then treating them with an aqueous solution of a quaternary alkyl ammonium compound, and finally drying them.

2. A process for imparting antistatic properties to fibers of a high molecular weight synthetic polymer selected from the class consisting of polyamides, polyesters and acrylonitrile polymers, the steps consisting essentially of treating the fibers with an aqueous solution of polyacrylic acid at a temperature less than 100 C., thereafter drying the thus pretreated fibers, subsequently heating them to an elevated temperature above 100 C., then treating them with an aqueous solution of a quaternary alkyl ammonium compound, and finally drying them.

3. A process for imparting antistatic properties to polyamide fibers, the steps consisting essentially of treating the fibers with an aqueous solution of polyacrylic acid at a temperature less than 100 C., thereafter drying the thus pre-treated fibers, subsequently heating them to an elevated temperature above 100 C., then treating them with an aqueous solution of a quaternary alkyl ammonium compound, and finally drying them.

4. A process for imparting antistatic properties to polyethyleneterephthalate fibers, the steps consisting essentially of treating the fibers with an aqueous solution of polyacrylic acid at a temperature less than 100 C., thereafter drying the thus pre-treated fibers, subsequently heating them to an elevated temperature above 100 C., then treating them with an aqueous solution of a quaternary alkyl ammonium compound, and finally drying them.

5. A process for imparting antistatic properties to polycaprolactam fibers, the steps consisting essentially of treating the fibers with an aqueous solution of polyacrylic acid at a temperature less than 100 C., thereafter drying the thus pro-treated fibers, subsequently heating them to an elevated temperature above 100 C., then treating them with an aqueous solution of a quarternary alkyl ammonium compound, and finally drying them.

References Cited in the file of this patent UNITED STATES PATENTS 2,130,212 Watkins Sept. 13, 1938 2,253,146 Spanagel Aug. 19, 1941 2,343,095 Smith Feb. 29, 1944 2,421,363 Young May 27, 1947 2,500,122 Dixon Mar. 7, 1950 2,662,032 Uhlig et a1. Dec. 8, 1953 2,741,568 Hayek Apr. 10, 1956, 2,808,349 Melamed Oct. 1, 1957 2,840,546 Yost June 24, 1958 2,843,573 Melamed July 15, 1958 OTHER REFERENCES Neville et al.: Wetting Agents in Textile Processing, American Dyestuff Reporter, vol. XXII, Sept. 11, 1933, pp. 541, 542 and 543.

McCutcheon: Synthetic Detergents, Soap and Sanitary Chemicals, August 1949, pp. 39 and 40. 

1. A PROCESS FOR IMPARTING ANTISTATIC PROPERTIES TO HIGH MOLECULAR WEIGHT SYNTHETIC POLYMERIC FIBERS, THE STEPS CONSISTING ESSENTIALLY OF TREATING THE FIBERS WITH AN AQUEOUS SOLUTION OF POLYACRYLIC ACID AT A TEMPERATURE LESS THAN 100* C., THEREAFTER DRYING THE THUS PRE-TREATED FIBERS, SUBSEQUENTLY HEATING THEM TO AN ELEVATED TEMPERATURE ABOVE 100* C., THEN TREATING THEM WITH AN AQUEOUS SOLUTION OF A QUATERNARY ALKYL AMMONIUM COMPOUND, AND FINALLY DRYING THEM. 